Piezoelectric Fibers with Uniform Internal Electrode by Co-Extrusion Process

Piezoelectric fibers with internal electrodes were fabricated by the co-extrusion process. The initial feedrods, which were composed of an outer piezoelectric PZN–PZT layer, a thin conducting PZN–PZT/Ag layer inside, and fugitive carbon black at the center, were co-extruded through a reduction die (1 mm) to form a continuous fiber. After thermal treatment and sintering, the PZN–PZT/Ag layer became the inner electrode, while the carbon black at the center was removed by oxidation to form an empty space. Three different types of fibers were produced: (i) solid fiber filled with an inner electrode, (ii) hollow fiber clad with a uniform inner electrode, and (iii) hollow fiber clad with a partial inner electrode. The piezoelectric properties of the fibers were evaluated in terms of their longitudinal strain (s₃₁) or transverse displacement. When the dimensions of the fiber were 840 μm (outer diameter) × 420 μm (inner diameter) × 40 mm (length), the longitudinal strains of the solid fiber with the inner electrode and hollow fiber clad with the uniform inner electrode were 5.25 × 10⁻⁵ and 8.5 × 10⁻⁵ m/m, respectively, under an applied voltage of 100 V (0.48 kV/mm) at a frequency of 100 Hz. For the hollow fiber clad with a partial inner electrode with the same dimensions, the transverse displacement was 80 μm under the same applied electric field.     

Detection of Morganella morganii,a prolific histamine former,by the polymerase chain reaction assay with 16S rDNA-targeted primers

A polymerase chain reaction (PCR) assay for the rapid and sensitive detection of the most prolific histamine former, Morganella morganii, was developed. 16S rDNA targeted PCR primers were designed, and the primer specificity and sensitivity of the PCR assay were evaluated. The 16S rDNA sequence (1,503 bp) for M. morganii showed 95% identity to those for enteric bacteria, i.e., Enterobacter spp., Klebsiella spp., Citrobacter spp., Hafnia alvei, Proteus spp., and Providencia spp. The unique primers for M. morganii were designed on the basis of the variable regions in the 16S rDNA sequence. The primers showed positive reactions with all M. morganii strains tested. However, PCR amplification was not detected when the primers were tested with other enteric or marine bacteria. When the sensitivity of the assay was evaluated, M. morganii was detected at levels ranging from 10(6) to 10(8) CFU/ml in albacore homogenate after the PCR amplification. The sensitivity of the assay was greatly improved with the enrichment of samples, and 9 CFU of M. morganii per ml of albacore homogenate was detected after 6 h of enrichment at 37 degrees C.     

Development of immunoassay for detection of meat and bone meal in animal feed

An immunoassay system was developed for efficient detection of prohibited meat and bone meal (MBM) in animal feed. Monoclonal antibodies (MAbs) were raised against bovine smooth muscle autoclaved at 130 degrees C for 20 min. Among the 1,500 supernatants of hybridoma cells screened, MAbs 3E1, 1G3, and 3E10 were selected and characterized in this study. The first set of MAbs produced, 3E1 and 1G3, had stronger reactivity against MBM than against smooth muscle that was heat treated at 90 degrees C for 10 min. However, reactivity gradually increased against smooth muscle that was autoclaved at 130 degrees C for up to 1 h. The enzyme-linked immunosorbent assay for detection of MBM in animal feed was optimized with the MAb 3E10 because of its superior performance. MAb 3E10 diluted to 100-fold was used to differentiate bovine MBM from that of other species in ingredients used for commercial animal feeds and could detect down to 0.05% MBM mixed in animal feed.     

Piezoelectric Properties of PZT-Based Ceramic with Highly Aligned Pores

Porous lead zirconate titanate–lead zinc niobate (PZT–PZN) piezoelectric ceramics with a high degree of pore alignment were fabricated using directional freeze casting of a ceramic/camphene slurry. Well-aligned pores were formed as the replica of the camphene dendrites that grew in a preferential orientation, while a high porosity of 90% was achieved by employing a low initial solid loading of 5 vol%. As the orientation angle of the pores to the poling direction was decreased, the hydrostatic piezoelectric properties, such as hydrostatic piezoelectric strain coefficient ( d _h), the hydrostatic piezoelectric voltage coefficient ( g _h), and the hydrostatic figure of merit, increased significantly. The sample containing pores aligned parallel to the poling direction showed an extremely high HFOM of 161019 × 10⁻¹⁵ Pa⁻¹, which was ∼1300 times higher than that (124 × 10⁻¹⁵ Pa⁻¹) of the dense sample, owing to the presence of aligned pores.     

Fabrication of Porous PZT–PZN Piezoelectric Ceramics With High Hydrostatic Figure of Merits Using Camphene-Based Freeze Casting

Porous lead zirconate titanate–lead zinc niobate (PZT–PZN) piezoelectric ceramics with interconnected pore channels were fabricated using the camphene-based freeze-casting method. In this method, warm PZT–PZN/camphene slurries with various solid loadings (10, 15, 20, and 25 vol%) were prepared by ball milling at 60°C and then cast into molds at 20°C, resulting in the formation of solidified green bodies comprised of three-dimensionally interconnected camphene dendrite networks and concentrated ceramic particle walls. After the removal of the frozen camphene via sublimation, the samples were sintered at 1200°C for 2 h. All of the fabricated samples showed highly porous structures, consisting of fully dense PZT–PZN walls without defects, such as cracks or pores. As the initial solid loading was decreased from 25 to 10 vol%, the porosity was linearly increased from 50% to 82%. This increase in the porosity led to a reduction in the permittivity, a moderate decline in the d ₃₃ value, and a rapid decline in the d ₃₁ value, which endowed the porous samples with a high hydrostatic figure of merit (HFOM). The highest HFOM value of 35650 × 10⁻¹⁵ Pa⁻¹ was achieved for the sample with a porosity of 82%, as well as ɛ₃₃=284, d _h =298 pC/N, and g _h =118 × 10⁻³ V·(m·Pa)⁻¹.     

Piezoelectric linear motor with unimorph structure by co-extrusion process

A new piezoelectric linear motor was developed using a ring-shaped, unimorph stator composed of a piezoelectric active layer (0.3PZN–0.7PZT/Mn) and a conductive passive layer (0.3PZN–0.7PZT/Mn/Ag). The stator was prepared by co-extrusion followed by the thermoplastic green machining (TGM) process. After co-extruding the piezoelectrically active and passive layers together, they were machined into a ring shape and then sintered at 930 °C for 4 h. The stator was poled in the thickness direction and operated in radial vibration mode. A glass rod was used as the moving shaft. When a saw-tooth electric field was applied, the shaft moved linearly as a result of the stator's bending motion. When an inverted saw-tooth electric potential was applied, the shaft moved linearly in the opposite direction. The velocity of the piezoelectric linear motor was about 4 mm/s at an applied voltage of 80 V_p–p and a resonance frequency of 36.5 kHz.     

Histamine and Other Biogenic Amines and Bacterial Isolation in Retail Canned Anchovies

ABSTRACT: Histamine and biogenic amine contents in retail canned anchovies were determined. Bacterial strains were isolated, and their histamine-producing capability was determined. The majority of canned anchovy products (80%) had histamine levels below the FDA guideline of 50 ppm. The sensory quality of products was relatively good. A few samples contained high levels of histamine (>1000 ppm). Overall, histamine contents in the products showed great lot-to-lot variations. Spermine and tyramine were commonly detected in all samples analyzed, regardless of their histamine contents. Bacterial counts in the products were mostly below the detection limit (10² CFU/g), and bacteria were frequently recovered with the enrichment of test samples in tryptic soy broth supplemented with 0.5% or 5% NaCl. Only Bacillus spp., the nonhistamine formers, were isolated from these test products. Prolific histamine-forming bacteria were not detected in these canned anchovies.     

Molecular characterization of multidrug-resistant Proteus mirabilis isolates from retail meat products

Sixty-four multidrug-resistant isolates of Proteus mirabilis were collected from retail meat products in Oklahoma. The isolates showed four different patterns of antibiotic resistance based on their resistant phenotype and genotypes. Most of these isolates were resistant to ampicillin, tetracycline, gentamycin, and kanamycin. Class 1 integrons were detected as a common carrier of the antibiotic-resistant genes, such as aadA1, aadB, and aadA2. A few isolates (9%) contained class 2 integrons with three gene cassettes included: dhfr1, sat1, and aadA1. These isolates were even resistant to nalidixic acid due to mutations in gyrA and parC. All ampicillin-resistant isolates contained blaTEM-1. Plasmids that contained class 1 or 2 integrons and blaTEM-1 were able to be transferred from P. mirabilis isolates into Escherichia coli by conjugation, indicating that conjugal transfer could contribute to the dissemination of antibiotic resistance genes between the Enterobacteriaceae species.